The present invention relates to conveyor systems for movement of load-carrying carts. The invention is particularly useful for the conveyance of load-carrying carts between vertically separated floors, but can also be usefully applied to the conveyance of such carts horizontally. The system is useful in a wide variety of applications, such as transit terminals, supermarkets, warehouses, etc., as well as for a variety of industrial applications. The present invention employs technology of the Weller U.S. Pat. No. 3,655,013, and of European Patent No. 0,012,149, but constitutes an improvement over such technology.
Currently, the principal means for moving load-carrying carts from one elevation to another have been elevators, inclined moving walks, conventional escalators, and also special cart conveyors of the type described in the before-mentioned Weller U.S. patent. All such prior systems have had certain disadvantages, which are obviated by the present invention.
Until the present invention, elevators have offered the safest method of moving loaded carts from floor to floor. But taking into consideration the elevator floor space occupied by a cart and its attendant, the elevator capacity required to handle a large volume of traffic is such that this technique is both unrealistic and unacceptable for most purposes.
Inclined moving walks are used in some cases for moving carts and their attendants from place to place. However, such moving walks are not very suitable for moving carts from one vertical level to another. For one thing, safety codes require the inclination of the moving walk to be very low, so that extensive space is required for a given amount of change in elevation. In addition, there can be significant safety considerations because of possible run-away carts, etc.
It has also been proposed to provide specially designed carts that can be moved onto conventional passenger-carrying escalators, which typically can convey passengers at an angle of 30-35.degree.. This, however, is regarded as a particularly dangerous technique for conveying of loaded carts because of the possibility of load shifting on the carts, tilting or jamming of the carts or the like.
The cart conveyor system of the before-mentioned Weller U.S. Pat. No. 3,655,013 is designed to allow a cart to be carried up or down a substantial incline, while the cart is retained in a more or less horizontal orientation. These conveyors are intended to be operated in parallel with passenger escalators or alongside stairways, for example, allowing the loaded carts to be placed on the special cart conveyor at one level and then retrieved at the next level, the passenger or cart attendant having either walked or been conveyed to the second level. The Weller U.S. Pat. No. 3,655,013 represented a significant advance in cart conveyor systems, particularly in recognizing the desirability of employing laterally opposed conveyor bands for engagement of the cart on opposite lateral sides. Nevertheless, the overall design of the Weller conveyor system has certain limitations which render its performance less than optimum for many applications.
In accordance with the present invention, a novel and improved cart conveyor system is provided in which both the cart and the conveyor are specially designed and adapted for each other to provide for highly efficient, safe conveyance of the carts, either upward or downward between different floor levels, or even along the same floor level where appropriate. To particular advantage, the carts and the conveyor mechanisms of the new system are mutually designed such that load-carrying platforms of the carts can be located very low on the cart, and preferably at a level which is little if any above the level of the wheels of the cart. This has one important advantage of maintaining the center of gravity of the loaded cart as low as practicable. Additionally, many carts of the existing conventional design, such as luggage carts frequently found at airports and other passenger terminals, are constructed with load-carrying frames providing not only a low center of gravity but also permitting lateral projection or overhang of the load items. The system of the present invention readily accommodates the design of its carts to be compatible with the load-carrying configuration of carts of the type which are currently used and accepted for conventional use on a level surface. In addition, carts constructed in accordance with the invention may in a practical manner be provided with physical structure, in the form of baskets, platforms or other load-carrying framework that itself projects laterally beyond the wheels of the cart and over the tops of the laterally opposed conveyor bands without compromising the safety of the system. This is made possible in part because the mutual design of the carts and conveyor mechanisms allows the load-carrying elements of the cart to be kept as low as possible to the ground, and also provides for laterally projecting portions of the load, and/or the load-carrying elements, to be guided and supported over the top of the conveyor bands during the conveying operation.
In accordance with another aspect of the invention, the design of the carts and conveyors is such that the load-carrying platforms, at least portions of which are at a minimum elevation, at or near the level of the wheels of the cart, nevertheless provide for and accommodate lateral protrusion of the load from the load-carrying platform. To this end, the system of the invention, which includes laterally opposed conveyor bands, engageable with the carts on opposite sides, provides for the conveyor bands to be positioned at the lowest practicable level, typically and preferably within the height of the wheels. In addition, housings for the conveyor bands are also located as low as practicable in order to accommodate the projection of load items, such as duffel bags and the like, laterally outward from the carts and over the tops of the conveyor band housings.
Load-carrying carts pursuant to the present invention are especially designed and constructed for cooperation with a conveyor mechanism as generally described in the preceding paragraph. Such carts typically have a pair of widely spaced, non-swivelling wheels at one end, typically the back end, and ones or more swivel-mounted wheels at the opposite end. Where a single swivel wheel is employed, it typically is mounted along the center line of the cart. If a pair of swivel-mounted wheels is employed, they typically are spaced symmetrically with respect to the center line of the cart, spaced apart a distance less than the spacing of the fixed wheels. The conveyor system is provided with separate wheel tracks for the front and back wheels of the cart. In addition, as shown in the before-mentioned patents, where the conveyor is inclined, the guide tracks for the respective front and back wheels are offset horizontally such that, when the cart is ascending or descending the conveyor path, the cart is maintained or more less in a horizontal orientation, preferably tilted slightly upward at the front. In addition, in accordance with the present invention, means are provided at the front of the cart for engagement with a retaining track extending along the conveyor path, which locks the front of the cart against vertical movement with respect to the conveyor path such that the cart, which is being engaged at the back by opposed conveyor bands, is prevented from tipping. Where a single front wheel is employed, the retaining means may be integrated with the wheel mounting structure. Where a pair of front wheels is provided, it may be more expedient to employ a separate retaining element, positioned to engage a central retaining track, running the length of the conveyor path.
The principles of the invention are applicable to a wide variety of cart constructions and configurations, including carts with free running wheels, carts with automatic or manual brake systems.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of preferred embodiments thereof and to the accompanying drawings.